Only a few hundred years ago, the night sky was seen as the interior of a large sphere to which the stars stick – somewhat similar to the projected spots of light on the planetarium’s dome. It wasn’t until the sixteenth century that we realized that the universe has a third dimension: depth.
We are now aware of this in our solar system. Sometimes there is a beautiful coupling between the moon and Jupiter in the night sky, but in reality, the two celestial bodies of course are not close to each other. Soon Jupiter is two thousand times away, and the conjunction is clear.
This interesting image shows that the effect of cosmic depth is stronger. The image, recently taken with the Hubble Space Telescope, shows a bright star with a spiral galaxy directly below it. However, they have nothing to do with each other. The star is part of our Milky Way galaxy and is probably less than a thousand light-years away.
However, the galaxy (UGC 3855) is about 150 million light-years away – hundreds of thousands of times away. It is a huge group of tens of billions of stars, comparable to our Milky Way. It’s as if a dim LED is directly in front of you, while you can see the glow of an entire city tens of kilometers away.
The star’s four diagonal “rays” are caused by the diffraction of starlight in the telescope. You see something similar when you narrow your eyes to a bright, point-shaped light source.